Various types of systems to prevent knocking operation of an internal combustion engine (ICE) are known, see for example the referenced U.S. Pat. No. 4,133,475, HARNED as well as the referenced applications Ser. No. 410,629, filed Aug. 23, 1982, BONITZ, now U.S. Pat. No. 4,478,068, and Ser. No. 419,933, filed Sept. 20, 1982, BRITSCH, the latter two being assigned to the assignee of the present application, and the disclosure of which is hereby incorporated by reference.
The control systems described in the referenced patents control the operation of an ICE in such a manner that knocking operation is prevented. This control can be accomplished by either setting the ignition instant to delayed or retarded point, controlling change in the fuel-air composition, or, otherwise, controlling the operating parameters of the engine. The systems of the references are so arranged that, if knocking operation is sensed, the engine operating conditions are changed until no knocking is sensed anymore; after a predetermined period of time has elapsed in which the engine operates under non-knocking conditions, the engine operating parameters are again changed so that the engine will operate under its best or most efficient operating conditions, which may be just below the knocking level. The resetting of the engine operating conditions is carried out, as described, in small steps, until the conditions under which the engine should be operated again have reached those which are set by an engine controller, for example. Signal processing of knocking signals sensed by a knock sensor is preferably carried out by comparison with a reference signal, see for example the referenced U.S. Pat. No. 4,478,068. The ignition timing can be changed, but other engine operating parameters which affect engine knocking may likewise be modified. For example, if knocking operation is sensed, the fuel-air ratio can be changed to a richer mixture, if the engine is of the fuel injection type, the injection instant can be changed or, for example, if it includes a turbo supercharger, the turbo pressure can be lowered. Other changes in the operating conditions may also be made, for example addition or injection of additional substances to increase the knocking resistance of the fuel-air mixture; the exhaust gas recirculation (EGR) system can also be modified.
The operation of an ICE is set, for example by an engine or vehicle computer, for most efficient and efficacious operation. If knocking is sensed, and the operating conditions changed, it is desirable to return to the preset or precomputed operating conditions as soon as possible, which is done in accordance with the systems described in the referenced patent and applications, in small steps. The return to normal operating conditions should be such that the effect on operating performance of the engine is gentle and does not introduce jolts or jars. The change in operating condition is commanded in the same direction, for example as a function of engine speed and/or intensity of sensed or incipient knocking.
It has been found that under transient conditions of operation of the ICE, for example under conditions of rapid acceleration, rapid change in loading or the like, return to normal operating conditions in small steps is too slow. The return to normal operating conditions, if stationary or quasi-stationary parameters have changed, is appropriate; under transient conditions, however, the desired or ideal value of the function which was modified, for example ignition timing, can be changed too much, or too fast, so that slow, stepwise return to the initial value is not desirable, since the engine will operate for a considerable period of time under less than ideal or commanded conditions.